Well, that article can be wrong. They are even talking about a 4th WC. But I'm quite sure the entry list which smucav posted is the official one. And Haas is still on it. He most likely just forgot to withdraw
Petzschner is a WC for sure as Vliegen would have been the next alt. The entry list is referring to the ranking from six weeks ago when Petzschner was ranked way too low for a direct entry.